Modified Preparation Of PbO₂ Electrode And Its Electrocatalytic Degradation For Triazine Herbicides

The PbO₂ electrode has been widely used in electrocatalytic degradation of organic wastewater due to its high electrocatalytic activity and corrosion resistance.In this work,Bi-PbO₂ electrode and PbO₂/WO₃ composite electrode were prepared by modifying the lead dioxide electrode with doping metal bismuth ions and composite WO₃ nanoparticles,respectively,which were applied them to the electrocatalytic degradation of triazine herbicides.Bi-PbO₂ electrode was prepared by electrodeposition method.The results of SEM and XRD analysis showed that the coating of Bi-PbO₂ electrode was denser and the grain size was smaller.Moreover,the electrochemical test showed that Bi-PbO₂ electrode had higher oxygen evolution overpotential than pure PbO₂ electrode.Bi-PbO₂ electrode was used as the anode for electrocatalytic degradation of cyclazinone,and the main factors affecting the electrocatalytic degradation of cyclazinone were analyzed: initial concentration of cyclazinone,current density,initial p H value,Na₂SO₄ concentration of electrolyte.The results showed that the electrocatalytic degradation of cyclazinone conformed to the pseudo-first-order kinetic model.The removal rate of cyclazinone could reach 99.9% after the Bi-PbO₂ electrode was used as the anode for the degradation of 120 minutes.Compared with the pure PbO₂ electrode,the Bi-PbO₂ electrode had higher removal rate of cyclazinone and COD,higher ICE value and lower energy consumption.In addition,the mechanism of electrocatalytic degradation of cyclazinone by Bi-PbO₂ electrode was also studied.Fifteen intermediates produced in the process of degradation of cyclazinone were analyzed by HPLC-MS,and two parallel sub-pathways of the possible degradation pathway of cyclazinone were clarified.PbO₂/WO₃ composite electrode was prepared by composite electrode position method.The effects of WO₃ particles on the surface morphology,structure and electrochemical properties of lead dioxide electrodes were investigated.Compared with PbO₂ electrodes,the introduction of WO₃ particles could decrease the grain size of lead dioxide and form compact and fine surface structure.Electrochemical measurements demonstrated that PbO₂/WO₃ composite electrodes owned higher oxygen evolution overpotential,larger electrochemical active surface area and stronger hydroxyl radicals generation performance than PbO₂ electrodes.The service life of PbO₂/WO₃ composite electrodes（131 h）was 3.74 times longer than that of pure PbO₂ electrodes（35 h）.Effect of key operating parameters,such as current density,the initial metribuzin concentration,the initial p H values and supporting electrolyte concentration,on electrochemical degradation of metribuzin were studied.Particularly,the current density and initial metribuzin concentration exerted prominent effects on electrochemical degradation of metribuzin.Moreover,kinetic analysis indicated that the electrochemical degradation of metribuzin was a pseudo-first-order reaction.The intermediates in the degradation of oxazinone were identified by hplc-ms,and some aromatic intermediates and inorganic ions were obtained.Finally,the electrochemical degradation pathway of metribuzin in aqueous solution at the PbO₂/WO₃ composite electrode was proposed based on the identified reaction intermediates.